There have been reports of fresh shelling in Nagorno-Karabakh, just hours after a ceasefire between Armenia and Azerbaijan came into force.
Blasts hit Stepanakert, the disputed region’s capital, on Saturday evening, say eyewitnesses and Armenian media.
Both sides had previously accused the other of continuing bombardments in other areas.
After two weeks of fighting, the two countries agreed to a temporary truce during talks in Moscow on Friday.
The now-fragile ceasefire was to allow the two countries to exchange prisoners and recover bodies from the recent bout of fighting.
More than 300 people have died and thousands been displaced since the latest violence in the long-running conflict broke out on 27 September.
Nagorno-Karabakh is run by ethnic Armenians although it is officially part of Azerbaijan.
The two former Soviet republics have blamed each other for the latest outbreak of violence – the worst in decades.
Meanwhile US celebrity Kim Kardashian West, who is of Armenian heritage, announced on social media that she was donating $1m to a fund for Armenian victims of the conflict.